| From | Message |
Dan M
Dodge Dakota
JOIN HERE
10/21/2004
18:11:06
|
 Subject: Really bad highway MPG
IP: Logged
Message:
I have a '95 CC 4x4 with 3.9L auto. New tires (2 months old) with alignment when installed, New autolight 3924 plugs, new autolight wires. New PCV, new oxygen sensor. Cat is 10 months old, muffer older. I passed emission testing 3 months ago with flying colors.
my daily commute is about 20 minutes in city, max speed 45. A few stop lights, not much long stop and go traffic. If I do not drive on the highway at all, I get ~16.5 (give or take .2MPG) MPG. If I drive on the highway, even for 30 miles (max speed of 75, avg around 70), my mpg is 13-14.5. If I drive for more on the highway, the worse gas milage I get. When i get 16.5, I usually do some city driving around with alot of stop and go speeds up to 60 mph.
can driving even 30 miles at 75 cause that big a decrease in mpg? 2 MPG lower? That seems a bit much for even such a short distance.
- Dan M
|
Bob Lincoln
Dodge Dakota
JOIN HERE
10/21/2004
22:24:49
| RE: Really bad highway MPG
IP: Logged
Message:
What is the engine speed at 65 mph? You should be at 1800 RPMs with the 4-speed auto and 3.55 axle. If at 2600 RPMs, you're in 3rd and not O/D. Does your O/D engage?
|
?
Dodge Dakota
JOIN HERE
10/22/2004
08:33:24
| RE: Really bad highway MPG
IP: Logged
Message:
95 ? means it has EGR valve/solenoid ??
At back of engine passenger side !
Replace it ... about 50 to 60 bucks
comes as assembly.
It is probably staying too activated at
highway speeds......
|
MY H3RO
Dodge Dakota
JOIN HERE
10/22/2004
10:19:30
| RE: Really bad highway MPG
IP: Logged
Message:
Dan M
I had the same problem with my 03. Put a tonneau cover on and your mileage will go waaaaay up
I remember someone saying that a Dak has the aerodynamics of a barn door.
Ken
|
?
Dodge Dakota
JOIN HERE
10/22/2004
12:43:19
| RE: Really bad highway MPG
IP: Logged
Message:
Tonneau may help , but EGR is problem..
Highway mileage should increase because of steady runnning , NOT decrease..
|
MY H3RO
Dodge Dakota
JOIN HERE
10/22/2004
15:17:51
| RE: Really bad highway MPG
IP: Logged
Message:
Wind Resistance. That tailgate is a DRAG
|
android287
GenIII
10/22/2004
19:01:54
| RE: Really bad highway MPG
IP: Logged
Message:
i get my best highway mpg cruising at 65. Once i start hitting 75 it really starts to go downhill.
|
Bob Lincoln
Dodge Dakota
JOIN HERE
10/22/2004
19:12:35
| RE: Really bad highway MPG
IP: Logged
Message:
EGR may be faulty, but I'd test it first; don't blindly replace it on a hunch.
Mileage plummets at higher speeds. At 65, I get 20 mpg. At 75, I get 17 or less. No big mystery there. But you should get better mileage at 65 than in city driving.
I have a cap that's level with the cab, helps aerodynamics more than the extra weight hurts.
|
Dan M
Dodge Dakota
JOIN HERE
10/22/2004
19:36:41
| RE: Really bad highway MPG
IP: Logged
Message:
I forgot to mention that I do have a tonneau cover on, have had it on since a few months after I bought the truck.
I just read over the EGR section in the haynes manual and that seems to be the issue. The truck does idle rough.
thanks for the info
- Dan M
|
Bob Lincoln
Dodge Dakota
JOIN HERE
10/22/2004
21:37:35
| RE: Really bad highway MPG
IP: Logged
Message:
Ah. You didn't say that. Sometimes a clogged cat will back up and ruin the EGR valve.
|
Dan M
Dodge Dakota
JOIN HERE
10/23/2004
00:18:51
| RE: Really bad highway MPG
IP: Logged
Message:
I doubt it's the cat. It's only 10 months old, besides that, it was running rough at idle before the cat was replaced and after too. It idles rough sometimes and sometimes it does not. After reading the haynes manual, a bad EGR makes sense.
However the old cat i had one was pretty bad, it may have contributed to the EGR failing. The rough idle issue is one i've been trying to track down for 1+ year. I've taken it to various dealers and independents for tests, inspects, etc and noone has found any reason for it as of yet.
I really don't know when the poor gas milage started, i didn't pay attention until the last few months.
thanks for the input all
-Dan M
|
Bob Lincoln
Dodge Dakota
JOIN HERE
10/23/2004
09:49:02
| RE: Really bad highway MPG
IP: Logged
Message:
But that's what I'm saying. The cat may have been bad, then took out your EGR and initiated the rough idle, then you replaced the cat with the EGR valve still being bad. The exact thing happened to my Dak when my brother owned it.
I'm not saying the new cat is bad, I'm saying the old one may have wiped out your EGR and you didn't know all this time.
|
| | P 1 |
|
Post a reply to this message:
Username Registration: Optional
All visitors are allowed to post messages
|
